2. How is life on Earth protected from space radiation?
--Choose one--
A. Water vapor clouds in the atmosphere.
B. A thick atmosphere and a magnetic field.
C. Greenhouse gases, like carbon dioxide.

3. What would happen if the crust and mantle stopped moving?
--Choose one--
A. Volcanic activity would increase and Earth
would become very hot.
B. Carbon dioxide would not be released into
the atmosphere
and Earth would become very cold.
C. Space radiation would bombard Earth's
surface and
harm life.

4. If the Earth's mantle motion increased, what would happen?
--Choose one--
A. Volcanic activity would increase causing ash to fill the air.
B. Carbon dioxide would not be released into
the atmosphere.
C. Space radiation would bombard Earth's
surface.